If Hollywood movies such as "WALL-E" have showed
anything, it's that humans are willing to believe that robots have feelings.
But creating a robot which can truly understand and respond to emotions remains
tricky for researchers.

Many robots can already pull off a decent job of imitating
emotion. MIT's Media Lab has created robots with faces, including Kismet,
Leonardo and most recently
Nexi, that can express various emotions in response to certain social
situations.

The illusion of a feeling, thinking being can break down,
though, when a robot or virtual human reaches a point known as the
"Uncanny Valley," caught between almost-human realism and doll-like
stiffness. That creepy "too-real" effect appears in Hollywood films
such as "The Polar Express" and "Beowulf," even as video
game makers have mostly steered clear of ultra-realistic characters to avoid
the problem.

"It turns out that, as human beings, we've developed
these incredible capacities to interact with each other using language and
visual, nonverbal behavior," said Stacy Marsella, a computer scientist at
the University of Southern California. "Without nonverbal behavior, it doesn't
look good — it looks sick or demented."

Marsella has been helping the U.S. Army develop artificial
intelligence (AI) that can power virtual training simulations. Such virtual
characters need to have the right facial expressions and body movements to
allow human trainees to feel comfortable interacting with them.

However, an even more difficult challenge lies in getting
the AI to actually understand what ideas and emotions a human is conveying —
and then process its own appropriate response.

The key lies with what psychologists call "theory of
mind," or the ability to perceive the intentions of another person (or AI
agent). AI under development at MIT and other places has only achieved the
first glimmerings of theory of mind, at least in simple situations such as
understanding that a researcher who wants potato chips is searching in the
wrong box.

Creating an AI that can carry on a sophisticated
conversation with humans remains difficult. The U.S. Army wants such AI to help
train soldiers to deal with complex social situations, such as mediating among
tribal elders in Afghanistan.

"Developing a virtual human is the greatest challenge
of this century," said John Parmentola, U.S. Army director for research
and laboratory management.

Marsella and other researchers working with Parmentola have
even floated the idea of someday testing their AI in online video games, where
thousands of human-controlled characters already run around. That would
essentially turn games such as "World of
Warcraft" into a huge so-called Turing Test that would determine
whether human players could tell that they were chatting with AI.

"I think eventually we'll be able to convince people
that they're interacting with a human," Marsella told LiveScience, but he added that he couldn't predict how long that
might take.

In Robot Madness,
LiveScience examines humanoid robots and cybernetic enhancement of humans, as
well as the exciting and sometimes frightening convergence of it all. Return
for a new episode each Monday, Wednesday and Friday through April 6.

Jeremy Hsu

Jeremy has written for publications such as Popular Science, Scientific American Mind and Reader's Digest Asia. He obtained his masters degree in science journalism from New York University, and completed his undergraduate education in the history and sociology of science at the University of Pennsylvania.